1. Technical Field
The present invention relates in general to video servers and in particular to buffering short clip video streams from video servers. Still more particularly, the present invention relates to buffering sufficient video assets during video streaming from a video server to prevent interruption of video streams due to data storage device underflow.
2. Description of the Related Art
Video servers are employed in a variety of contexts for providing streams of video information. (As used herein, the terms "video information" or "video assets" are intended to encompass video, including motion, stop-motion, or frame video, and combined video/audio information). The most common utilization is for broadcasting, either over conventional electromagnetic transmission or cable. Video assets of up to 10-15 hours are stored for streaming to the broadcast device. Video servers are also beginning to be widely employed for "Web-casting," transmission of video information over the Internet utilizing the World Wide Web format.
In video server systems, due to the nature of the underlying hardware and the real time response requirements of video streaming, it is necessary to maintain an adequate amount of video assets in short term memory buffers. Video data often originates from devices such as disk drives whose short term supply of data may fluctuate below the threshold necessary for proper streaming. For example, this can be caused by disk thermal recalibration or RAID (Redundant Array of Inexpensive Disks) data rebuild.
As a result of this data supply fluctuation, it is necessary to maintain data buffering equal to the real time streaming rate times the data storage device's maximum underflow time period. However, the device underflow time period may exceed the length of a single video clip. This easily happens with short video clips during failure of a RAID disk. In the short clip environment, it has been impossible or at least very expensive to maintain proper buffering to cover device underflow. Video streaming devices for the Internet or cable transmission typically have unique, specialized hardware solutions requiring a minimum video clip length to prevent underflow, and generally cannot handle subsecond video clips.
It would be desirable, therefore, to provide a method and apparatus for maintaining enough video data such that data storage device underflow would not result in underflow of the video decoder causing visible picture fluctuation.